It doesn't look like there is much rhyme or reason to your rock placement, slope and substrate line. Which can be fine depending on the look your going for. Looks like the start of a biotope to me, lacking a leaf littered bottom and driftwood.
What are your plans for the tank? Plants? If so what types?
I think you shouldn't use so many different types of rocks for starters. They are all very similar size except that one pointy guy middle left. When I look at your scape I see that pointy stone first then the rest all fall off and do nothing for the look. They are placed almost all equal distance from one another perfectly across the tank with the pointy sides of the stones into random directions left and right. I can see some placement choices where you fit them together but the look is not dramatic. A well done iwagumi can be kinda breathtaking, even before planting. I get that you might not be going for some really amazing looking iwagumi based off your rock choices. A lot of people spend a fortune on rocks to get that look. But I do think some better placement decisions will help bring your scape up a notch.
It helps to make one or two dramatic slopes with the substrate for the rocks to position on. Then place groupings of stones on the slope(s). Your substrate is very wavy and random. It looks almost like you just poured it in and that's that.
I would drain the tank, fix the substrate and then pick your favorite stones. Those you want to highlight. The remaining stones you can use in combo with one another to make a larger appearing stone or use to prop up other stones etc etc. I combine rocks in my layouts to make bigger rocks. See which rocks can fit together, almost like a puzzle.
Too many different kinds of rock.
Use only one kind of rock, and make them look more grouped, connected.
Think of it like this:
A big crust of rock has pushed its way up through the earth.
It has been eroded from wind and water over the years, but the rock has not broken apart. Whatever grain or layers there are should all point the same way. Whatever breakage has happened (leaving tall pointy parts) all happened in the same direction, leaving the main mass as it was. It is this main mass, partially buried in soil, that is usually the goal of a planted aquarium with rocks.
1) put a bed of substrate down that will support the rocks. Begin hills with deeper substrate, valleys with less. But this is more of a bottom cushion, just a hint of 'scaping.
2) Line up the rocks so all the grain or layers or breaks point the same way. Place some (tallest) toward the back. Place some near those tall ones, but in front. Most often these are done in 2 groups, similar but not the same size.
3) Put some up higher, some lower. Add substrate as needed to hold the rocks up.
4) Add more substrate, making the part against the glass front low and level. Make distinct valleys.